Manufacture of paper tubes



March 3, 1931.

W. H. WOODFORD MANUFACTURE OF PAPER TUBES Filed April 16, 1929 Fig. 1

Fig. 4

IN VEN TOR.

H. WOODFORD TORNEYS time! Mn, 3, 1931 UNITED STATES.

PATENT OFFICE WATSON H. WOODFORD, OF BRIDGEPORT, CONNECTICUT, ASSIGNOB TO REMINGTON ARMS COMPANY, INC., A CORPORATION OF DELAWARE MANUFACTURE or PAPER TUBES Application filed April 16,

The present invention relates to the manufacture -of articles of paper,- and more especially to wound paper tubes used in the manufacture of shot shells. In the manufacture of shot shells, tubes for shell bodies are customarily formed by winding a sheet of paper about a mandrel into a tube of approximately four-and-one-half wraps of paper. An adhesive, such as a starch paste, is usually applied to the paper during the winding operation. After winding, the tubes are stripped from the mandrel, are passed through rotarydies to be brought to a proper size, are dried,

and are subjected to several treatments for the purpose of rendering the tubes resistant against powder burns on discharge of the shot shell and for rendering the shot shells waterproof when exposed tomoisture.

A treatment commonly in use consists in dipping the tube in molten paraffin wax to impregnate the layers of paper with parafiin, in-order to provide the inner layers with a heat absorbent effective to take up enough of the heat of powder'combustion on discharge to prevent excessive charring of the paper of the tube. Paraffin so used effectively protects the tube against powder burns but does not render it adequately waterproof. In or- 9 der to effectually waterproof the shot shell it becomes necessary to coat the finished article with a waterproofing-substance; atask'very difficult of successful accomplishment on the surface of a parafiin-impregnated tube.

When such a lacquer is applied to a parafiined' surfa e a part of the lacquer may dry but a" Ithas been found that a very desirable.

1929. Serial No. 355,458.

substantial portion remains soft and tacky for an indefinite period. Apparently, what happens is that the paraflin is dissolved in the lacquer solvent andquickly reaches the surface, forming an impervious film over the wet lacquer and seriously retarding evaporation of the solvent. If this film be broken to permit evaporation of the solvent, the lacquer may dry, but a parafiin surface is formed and not. the desired lacquer surface.

In order to make possible the use of a lacquer as a highly eflicient waterproofing coat for the exterior of the shot shell, and at the same time enable the use of an. efli'ective substance to render the paper of the tube resistant against powder burns, attempts have been made to confine the heat absorbing substance to the inner wraps of the paper, leaving the surfaceof the tube free to ef-- fectually receive a lacquer coating. A successful method of accomplishing this end is disclosed in my co-pending application, Serial No. 203,445, filed July 5, 1927 (now Patent N 0. 1,7 67 ,827, June 24, 1930) wherein is taught the application of a heat absorbing substance to the middle portion of a sheet of paper before winding the paper-into a tube. In the wound tube the heat absorbing substance is confinedto the two middle wraps of the four or more wraps of paper and, being entirely. removedfrom. the outer. wrap does not affect the application of a lacquer to the tube. In the prior application is disclosed the use of petrolatum rather than paraffin as a heat absorbing substance because of the greater ability of petrolatum to prevent powder burns and also because of its greater flexibility, rendering the impregnated paper easier to wind into a tube. A shot shell constructed after the disclosure of my prior application is highly eflicient in resisting powder burns and at the same time presents an outer surface on which a waterproofing coat of lacquer may be effectually applied.

Although the method of my prior application has been used with a high degree of success, it is found that in the course of manufacture by quantity production methods it is diificult to prevent the accumulation of small quantities of petrolatum on the outside of the tube and,- inasmuch as petrolatum is a substance which repels the lacquer, an uneven lacquer surface is liable to form where such petrolatum accidentally gathers on the tube surface.

The present invention contemplates an improved paper tube shot shell and method for constructing the same wherein the above enmerated and other difliculties are avoided.

It is an object of the present invention to provide a shot shell having a paper tube body which is at once highly reslstant against powder burns and impervious to moisture.

It is a further object of the present invention to provide a wound paper tube, the wall of which has interior wraps which are treated with a heat absorbing substance and an outer wrap which is coated with a waterproofing lacquer.

It is a further object of the present invention to provide the wraps of a paper tube for shot shells with an eflicient heat absorb- 'ing substance, which substance on finding its way accidentally to the outer surface of the tube will not repel a lacquer applied thereon.

It is a further object of the present invention to provide a shot shell tube that is rigid and hard, permitting the formation of an efficient crimp at one end of the tube.

Other objects will appear from the following specification, of which the accompanying drawings form a part.

In the drawings:

Fig. 1 is a fragmentary plan View of a sheet of paper prepared for winding into a paper tube according to the present invention.

Fig. 2 is an enlarged section through the wall of a tube wound from such a sheet of paper as is shown in Fig. 1.

Fig. 3 is an elevation of a finished shot shell comprising a tube wound from paper prepared as illustrated in Fig. l, the wall of the tube being broken in such a way as to show its construction.

Fig. 4 is a fragmentary plan view of a sheet of paper similar to that shown in Fig. 1, but treated somewhat differently preparatory to windin Quic-l ily drying lacquers, whether of the spirit varnish type, pyroxlin lacquer type, or pyroxylin resin lacquer type, contain three essential ingredients:

1. A base comprising, for example, natural or synthetic gums, resins or low viscosity pyroxylin;

2. A quickly evaporatingsolvent, for example, of acetone, methyl alcohol, amyl acetate, ethyl acetate or benzine; and

3. A plasticizer, the purpose of which is to render the finished lacquer coat somewhat flexible and remove the undesirable characteristic of brittleness which the coat would have if a plasticizer were not used.

According to the present invention, a plasticizer is used not only as an essential ingredient in the waterproofin lacquer applied-to the outside of the tube, ut is used also by itself or with other materials, as will be explained hereinafter, as a heat absorbing substance applied to the inner wraps of the paper tube. I have discovered that numerous substances making'excellent plasticizer ingredients for lacquers are also highly efficient as heat absorbing materials and may be readily applied to paper tubes for this purpose. For example, such a plasticizer as castor oil forms an excellent heat absorbing substance capable of being readily impregnated in the paper of the tube and having in a high degree the flexibility necessary to facilitate winding of the paper into a tube. Blown castor oil, or castor oil through which air has been passed, preferably under the influence of heat, thereby partially oxidizing and thickening the oil, is especiall good for this use. It is more viscous than the ordinary oil and is therefore more readily controlled inapplying it to the desired section of the paper. Other plasticizers which serve very well as heat absorbents are dibutyl phthalate, tricresyl phosphate, ethyl abietate, butyl tartrate, castor oil, rape seed oil, or triphenyl phosphate. If such a heat absorbing su stance by accident should find its way to the outer surface of the paper tube, being in itself a plasticizer for lacquer, it would combine with the lacquer applied to the outer surface of the tube, rather than repel the same, thus permitting the formation of an effectual waterproofing coat on the shell.

' Referring to the drawings, Fig. 1 illustrates a portion of a sheet of paper prepared for winding to form a tube. Before winding, a portion 11 of the sheet is treated with a plasticizer. This portion 11 is of such width that when the paper is wound into a tube it will extend over substantially two complete wraps in the interior of the tube wall. The portion 10 of the paper is left free from any'treatment and forms a little more than one'complete wrap in the interior of the wound tube. The remaining portion 12 of the sheet, which forms slightly more than one wrap on the outside of the wound tube, is also left untreated. One side of this portion of the sheet may be colored if desired, according to the usual practice. The overlapping parts of the untreated portions 10 and 12 of the paper provide surfaces adequate for a sufficient amount of adhesion, when paste is applied, and the untreated portions of the sheet take up enough of the paste to form a stifl' and sturdy tube.

The majority of plasticizers remain in a liquid state at normal room temperatures and have a tendency to flow. When impregnated in a portion of a sheet of paper the tendency is for superfluous plastic'izer to spread to other portions of the paper and, although no great harm may result from this spreading or creeping, it is desirable to insure a uniform product by confining the heat absorbent to the portion of the'paper'to which it is applied. I have found that by combining a suit able resin with a plasticizer to form a heat absorbent this end may be obtained. For example, a mixture of a resin, such as a cumar, with a plasticizer, such as rape seed oil, in proportions varying from 70% cumar and 30% rape seed oil to 30% cumar and 70% rape seed oil, according to results desired, gives a heat absorbent which when applied to a portion 11 (Fig. 1) of the paper from which the tube is wound, is exceptionally effective as a protection against charring and does not spread or creep from the portion of the paper to which it is applied. A mixture of approximately 60% cumar and 40% rape seed oil has given excellent results. Cumar is in itself a highly efficient heat absorbent,

as is also the plasticizer rape seed oil, both being superior to paraffin which has long been used for this purpose. The cumar besides being a heat absorbent acts to prevent the plasticizer from'creeping; and the rape seed oil besides being a heat absorbent acts in its capacity as a plasticizer to render the heat absorbent flexible to facilitate winding the treated paper into a tube. Further, such a resin as cumar has good water resisting qualities, and in case of an accidental breakage of the outside lacquer coat the shell tube is additionally protected against the damages of moisture absorption. As heretofore explained, such a plasticizer as rape seed oil, on finding its way accidentally to the outside of the tube, would assist rather than hamper the application of a lacquer waterproofing coat. The above example is illustrative rather than restrictive, it being understood that other resins such, for example, as the dammars, the copals, or synthetic resins, may be substituted for cumar, and that other suitable plasticizers, heretofore mentioned, may be substituted for rape seed oil. The proportions of the mixture may be varied as desired, it beingremembered that with an increase in the proportion of plasticizer the treated portion of the paper is made more flexible but that if it is desired to eliminate the creeping tendency of the plasticizer'an adequate proportion of resin must be used.

It is within the contemplation of my invention to obtain still other advantageous results by the use of a plasticized-resin as a heatabsorbent in the treatment of paper tubes for shot shells. Instead of impregnating a plasticizer or plasticized resin in the portion of the paper forming the middle wraps, as heretofore explained with reference to F ig. 1, a plasticized-resin heat absorbent maybe applied in the form of a coat 17 on the under surface of the sheet of paper as indicated in of each wrap. As seen in Fig. 4, the coat may extend to within a. short distance from the edges of the sheet,'leaving the small uncoated margins 18 and 19 sufficient for a secure adhesion of the paper in the wound tube. By thus coating a large portion of the entire under side area of the sheet it will be seen that insufficient untreated area remains to take up much adhesive paste in winding. A certain amount of adhesive paste must be taken up by the paper in order to form a tube rigid and hard enough to take a good crimp 15 (Fig. 3), consequently, provision must be made for the paper to receive this necessary amount of paste, preferably during the tube with a plasticized resin naturally repels water and cannot take any amount of paste. However, I have found that by adding a small amount of a suitable material as a Water-retaining pigment to the plasticized resin a surface is provided which water can wet, thereby causing the coated surface to receive enough adhesive paste to make, after the usual drying and sizing operations, a rigid and hard finished tube. A substance which serves very well as such a pigment is sodium bicarbonate which in'itself attracts water and in addition is a useful ingredient in a heat absorbent substance because of its fireproof characteristics. An amount of approxi mately 10% by weight of sodium bicarbonate added to the plasticized resin has given good results. Other substances may be used equally well as a pigment for this purpose such, for example, as dextrin, and the proportion of such pigment added to the plasticized resin may be varied according to the amount of bstarch paste desired to be taken up by the tu e.

By the last discussed method of treating a sheet of paper preparatory to winding into a tube several important advantageous results are obtained. The inside surface of all the wraps of paper in the tube is coated with a highly water impervious coat which is also an effective protection against excessive charring of the paper. At the same time a tube is provided the outside surface of which is untreated and clean to take a final coat of waterproofiing lacquer. A small amount of the plasticizer will leave the plasprise four moisture. This characteristic will be briefly explained: Referring to Fig. 4:, if the coated paper of this figure be suddenly wetted an expansion will take place in the outer fibres of the uncoated portion of the paper while little or no expansion will take place in the coated suriface of the paper, thus causing the whole sheet to violently curl up with the coated surface on the inside of the roll. In the finished shotshell tube this tendency to curl up wil be manifested in a tightening of the wraps 0 the paper tending to reduce the diameter of he tube. If water should pene trate into the Wraps of the tube through an accidental break in the outside waterproof coating, instead of tending to expand rendering the shot shell oversize and useless, the tube would tend to contract or decrease in diameter,

In the finished shot shell, referring to Figs. 2 and 3, the paper tube body is seen to comwraps of paper. The paper may be prepared as described for Fig. 1 by treat ing the portion 11 with a plasticizer or with a plasticized-resin, leaving the portion 10 untreated to form the interior wrap of the tube and the portion 12 untreated to form the outside wrap of th tube; or the paper may be prepared before winding as described for Fig. 4: by applying to the underside of the whole sheet, except for the small untreated edge margins 18 an 19, a plasticized resin coat containing a p.ste retaining pigment. The finished shot-sh 1 body is made waterproof over the entire utside area of its body portion by dipping tho finished shot shell in lacquer and, after removal, suspending the shot shell in the position shown in Fig. 3 to allow excess lacquer to drain off. A portion of the lacquer in draining ofi will form a fillet of lacquer 14 (Fig. 8) between the shell crimp l5 and the top wad 16. This part of the shell, vulnerable to moisture absorption, is thus adequately protected by a heavy and impervious coating, and a continuous waterprpiofing coat is formed over the whole shell bo y.

W'hen'the shot shell is discharged in the gun, the heat absorbing substance in the inner wraps of thetube takes up a large por tion of the heat of combustion, keeping the temperature of the paper of these wraps, as well as of the outer wrap, below the temperature of charring. Thus, the shell body left in the gun after firing is not destroyed by charring but is of suliicient strength to remain intact and may be easily extracted and ejected.

It will be understood that the embodiments of my invention, shown and described, are illustrative rather than restrictive, and various changes may be made without departing from the invention as hereinafter claimed.

In the appended claims, the term lacquer plasticizer is to be understood as including thereby keeping its proper gauge.

any plasticizingmaterial or mixture of such materials of the classes mentioned in the foregoing specification, and the term plasticized resin is to be understood as including any mixture of a resin or resins as mentioned in the specification with-any one or more suitable plasticizers.

I-Iavingfully described my invention, what I claim is:

l. A shot shell comprising a paper tube 7 body having a portion of its wall impregnated with a heat absorbent comprising a lacquer plasticizer.

2. A paper tube having a lacquer plasticizer applied thereto.

3. A wound paper tube having a lacquer plasticizer applied to the inner wraps of the tube.

4. A wound paper tube having a lacquer plasticizer applied to the inner wraps of the tube and a lacquer applied to the exterior surface of the tube.

5. In a wound paper tube for shot shells, the combination of a heat absorbing lacquer plasticizer applied to the inner wraps of the tube and a waterproofing lacquer applied to the outer surface of the tube.

6. A paper shot shell having a portion of its wall impregnated with a lacquer plasticizer, and a coating of lacquer on its exterior r surface.

7 In the manufacture of paper tubes for shot shells, the method of protecting the tube against charring which comprises applying a lacquer plasticizer to a portion of the paper from which the tube is to be wound and then winding the tube.

8. In the manufacture of paper shot shells, the method of controlling charring of the paper under heat of powder combustion which comprises applying a lacquer plasticizer to the paper of the shell.

9. The method of making a waterproof paper shot shell protected against charring which comprises applying a lacquer plasticizer to the paper from which the tube is to be wound, then winding the tube and then applying a lacquer to the wound tube.

10. A paper shot shell tube protected from charringby a plasticized resin applied to the inner wraps of the tube.

11. A paper shot shell tube protected from charring by a plasticized resin applied to the inner Wraps of the tube and waterproofed by a lacquerapplied to the exterior surface of the tube.

12. A paper shot shell tube the inner wraps of which have applied thereto a plasticized resin-containing a water retaining pigment.

13. A paper shot shell tube protected againstcharring by a plasticized resi'ncontaininga water retaining pigment and waterproofedby alacquer applied to the exterior surface of the tube.

WATSON H. WOODFORD.

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